Valves play an important role in our everyday lives. Valves are integral to the operation of well-known fluid systems, such as showers, lavatories, and other systems and subsystems of plumbing structures in our homes. Valves are also integral to household appliances, including dishwashers, clothes washers, refrigerator icemakers, and others. Valves also form essential portions of outdoor water systems for watering plants and lawns, and even isolating a water main from a residence or business for maintenance and other purposes.
Further, valves play an unseen and accepted role in water treatment and distribution as well as sewage treatment facilities. Many different types of valves make up a portion of the infrastructure and social fabric of our daily lives, providing dependable service to the general public for decades.
Valves play an even more important role in industry. The pipeline and chemical processing industries would not exist without valves, yet the primary function of valves is to control flow of fluids. Valves control fluids with a low viscosity such as natural gas or fluids with a high viscosity such as hot tar in refineries. Fluids can be Newtonian such as water having little or no solids content or non-Newtonian such as coal slurry pipelines—which have high coal solids content.
Technology has changed the way valves are used. The advent of the programmable logic controller (PLC) has enabled capabilities within control valves that were nonexistent only a few years ago. Environmental regulations and health and safety regulations have required valves to be manufactured to higher quality standards, be more reliable, and easier to maintain.
Environmental regulations have changed the performance requirements of valves. Regulations now in effect require valves to operate and perform while maintaining a rigid standard for operating without leaking. In these regulatory programs, leaking valves must be maintained and repaired and records must be kept of the leaks found and the repairs made. Valves that cannot be fixed are placed on a shutdown list and repaired as a portion of a maintenance turnaround operation. In some cases, operating units must be shut down to effect repairs of leaking valves. If the leak percentages are too high for too long, valves are placed under a quality assurance program (QAP) that steps up the frequency for the checking for leaks and implements more stringent repair standards. More recent regulations require reporting for any release of volatile hydrocarbons to atmosphere and require annual reporting to the regulatory agencies for inclusion on the facility operating permit; these are known as recordable emissions and include all volatile organic compounds. Various regulations exist for volatile hydrocarbons based on their composition and can be any one of the following: volatile organic compounds (VOC's), hazardous air pollutants (HAP's), very hazardous air pollutants (VHAP's), highly reactive volatile organic compounds (HRVOC's), national environmental standard hazardous air pollutant (NESHAP's) and possibly more regulations based on more stringent local and state regulations.
In chemical processing industry facilities, elevated process temperatures make it difficult to maintain stem packing in control valves—constant stem packing leaks cause problems with leak percentages in leak detection and repair programs (LDAR) mandated in regulations and LDAR programs are required to maintain environmental permits. The present invention makes repair and/or replacement of these valves that have stem packing problems viable without having to resort to costly extraordinary repair methods.
Very small uncontrolled leakage of certain important commercial chemicals—notably benzene, butadiene, and others—must be reported due to the associated health hazards. Benzene and butadiene have a maximum quantity to be released to the atmosphere of 0.05 pounds—i.e. less than an ounce. Most of the facilities that handle benzene or butadiene have Title V permits and must self-report any violations. A Title V permit is a federal operating permit obtained under Title V of the Clean Air Act Amendments of 1990 and provisions in the act require the entity with the Title V permit to self-report violations of the Title V permit provisions.
One important application area of these requirements invention is the pipeline industry. Pipelines typically operate under the auspices of the Department of Transportation, however, there is a memorandum of understanding (MOU) between the United States Department of Transportation (USDOT) and the United States Environmental Protection Agency (USEPA), that the USEPA has jurisdiction over USDOT facilities in non-attainment areas. The USEPA divides regions in the USA that can meet ambient air quality standards as “attainment areas” and those regions that cannot meet ambient air quality standards “non-attainment” areas. The air quality standards are more stringent in “non-attainment” areas. This memorandum of understanding has changed the primary reporting agency for pipeline companies that operate in non-attainment areas—particularly those pipeline companies carrying finished products (SIC Code 4613) such as ethylene, propylene, butadiene, PP Mix (Propylene Propane Mix), and other products. In particular, both ethylene and propylene require extensive purging with the respective product due to the low concentrations of oxygen or nitrogen that can be present in the finished products and would violate the finished product specification. This means that any pipeline repair on the pipeline or valves in the pipeline can require days of downtime and considerable finished product has to be flared (burned) to atmosphere. In addition, pipelines interconnect the manufacturers of a particular chemical product to the next manufacturer in a chain of products, e.g., propylene is often further manufactured into propylene oxide in another facility say 60 miles away. Generally, pipeline valves isolate a given facility from the pipeline so that the facility can be shut down. However, when maintenance on the valve is required, the maintenance activities may shut down as many as thirty or forty plants within a given geographic area. The importance of being able to repair and maintain a valve while under pressure can save some major coordination problems and unnecessary downtime in multiple facilities. If one is unable to repair or maintain a valve under pressure, there is lost product, lost pipeline revenues, and adverse environmental impact. The present invention can mitigate many of these losses.
It is important to note that valves in pipeline service should be “full port” valves to allow the passage of pigs, swabs, brushes, and smart pigs through the pipeline for maintenance reasons. Generally, a full port valve is 0.125 inches larger than the size designation, e.g., a four inch (4″) valve full port opening would be 4.125 inches in diameter.
Thus, there remains a need in the art for a valve assembly which enables an inner valve to be maintained, repaired, or replaced without de-pressuring the line in which it controls the flow. Such a valve assembly could play an important role in reducing maintenance costs, protecting the health exposures of employees, and reduce environmental emissions.